Method of manufacturing piezoelectric microactuators having wrap-around electrodes

ABSTRACT

A method of manufacturing a piezoelectric microactuator having a wrap-around electrode includes forming a piezoelectric element having a large central electrode on a top face, and having a wrap-around electrode that includes the bottom face, two opposing ends of the device, and two opposing end portions of the top face. The device is then cut through the middle, separating the device into two separate piezoelectric microactuators each having a wrap-around electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/316,633 filed Jun. 26, 2014, which is a continuation of U.S. patentapplication Ser. No. 14/045,773 filed Oct. 3, 2013, now U.S. Pat. No.9,406,314, which claims priority from Provisional Patent Application No.61/709,573 filed Oct. 4, 2012, the disclosures of which are incorporatedby reference as if fully set forth herein.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates to the field of suspensions for hard disk drives.More particularly, this invention relates to a method of manufacturingpiezoelectric microactuators having wrap-around electrodes such as foruse in dual stage actuated (DSA) disk drive suspensions.

2. Description of Related Art

Magnetic hard disk drives and other types of spinning media drives suchas optical disk drives are well known. FIG. 1 is an oblique view of anexemplary prior art hard disk drive and suspension for which the presentinvention is applicable. The prior art disk drive unit 100 includes aspinning magnetic disk 101 containing a pattern of magnetic ones andzeroes on it that constitutes the data stored on the disk drive. Themagnetic disk is driven by a drive motor (not shown). Disk drive unit100 further includes a disk drive suspension 105 to which a magnetichead slider (not shown) is mounted proximate a distal end of load beam107. Suspension 105 is coupled to an actuator arm 103, which in turn iscoupled to a voice coil motor 112 that moves the suspension 105arcuately in order to position the head slider over the correct datatrack on data disk 101. The head slider is carried on a gimbal whichallows the slider to pitch and roll so that it follows the proper datatrack on the disk, allowing for such variations as vibrations of thedisk, inertial events such as bumping, and irregularities in the disk'ssurface.

Both single stage actuated disk drive suspensions and dual stageactuated (DSA) suspension are known. In a single stage actuatedsuspension, only voice coil motor 112 moves suspension 105.

In a DSA suspension, as for example in U.S. Pat. No. 7,459,835 issued toMei et al. as well as many others, in addition to voice coil motor 112which moves the entire suspension, at least one microactuator is locatedon the suspension in order to effect fine movements of the magnetic headslider to keep it properly aligned over the data track on the spinningdisk. The microactuator(s) provide much finer control and much higherbandwidth of the servo control loop than does the voice coil motoralone, which effects relatively coarse movements of the suspension andhence the magnetic head slider. A piezoelectric element or component,made of piezoelectric material, sometimes referred to simply as a PZT,is often used as the microactuator motor, although other types ofmicroactuator motors are possible. In the discussion that follows, forsimplicity the microactuator will be referred to simply as a “PZT,”although it will be understood that the microactuator need not be of thePZT type.

FIG. 2 is a top plan view of the prior art suspension 105 in FIG. 1. TwoPZT microactuators 14 are affixed to suspension 105 on microactuatormounting shelves 18 that are formed within base plate 12, such that thePZTs span respective gaps in base plate 12. Microactuators 14 areaffixed to mounting shelves 18 by non-conductive epoxy 16 at each end ofthe microactuators. The positive and negative electrical connections canbe made from the PZTs to the suspension's flexible wiring trace and/orto the grounded base plate by a variety of techniques including thosedisclosed in commonly owned U.S. Pat. No. 7,751,153 to Kulangara et al.

In assembling a DSA suspension, the process typically includes the stepsof: dispensing liquid adhesive such as epoxy onto the suspension and/orthe PZT; positioning the PZT into place on the suspension; and curingthe adhesive, typically by thermal curing, ultraviolet (“UV”) curing, orother curing methods depending on the adhesive used. DSA suspensionsoften include both conductive epoxies and/or non-conductive epoxies tobond the PZT to the suspension. Conductive adhesives, such assilver-containing epoxies, are well known and are commonly used.

FIG. 3 shows a prior technique for bonding two PZTs in a DSA suspensionincluding the electrical connection therebetween. FIG. 3 is not admittedas being “prior art” within the legal meaning of that term. Similarly,the processes described herein as applicable to FIG. 3 are also notadmitted as being “prior art” within the legal meaning of that term.FIGS. 4 and 5 are cross sectional views taken along section lines C-C′and D-D′ in FIG. 3, respectively, showing the details of the bonding. Asbest seen in FIG. 4, the PZT 330 has electrodes on both sides where thebottom electrode is grounded at one end by conductive epoxy 324 throughgold 326 on grounded stainless steel 328 layer, and insulated at theother end by non-conductive epoxy 320. As best seen in FIG. 5, the topelectrode is connected to a copper electrical contact pad 316 which ispart of the suspension's electrical interconnect or flexible circuit andis insulated from the stainless steel substrate 312 by insulating layer314 such as polyimide, by conductive epoxy 322 over non-conductive epoxy320. Electrical contact pad 316 provides the driving voltage for PZT330. Non-conductive epoxy 320 is primarily responsible for themechanical bond between PZT 330 and stainless steel substrate 312. Ingeneral, the height of the conductive epoxy 322 for the top electrode isdifficult to control, and the overall PZT attachment process requiresthree epoxy bonding steps, which is time consuming and costly. Also, twoseparate curing steps are required for the epoxy on the bottom electrodeand on the top electrode.

There are drawbacks to the prior methods of bonding PZTs to suspensions.It can be difficult to control exactly how much epoxy is dispensed,where the adhesive ends up due to flow of the liquid adhesive, and otherissues. Various solutions have been proposed that involve, for example,channels underneath the PZTs to control the flow of adhesive and tochannel any excess liquid epoxy away from sensitive areas. U.S. Pat. No.6,856,075 to Houk, for example, proposes an adhesive attachment that hasone or more reliefs under or partially under or adjacent to a PZTtransducer to control the flow of adhesive by limiting or influencingadhesive travel or flow and simultaneously preventing excessive adhesivefillet height adjacent the piezoelectric motor. Additionally, if the PZTis located at or near the gimbal which carries the magnetoresistiveread/write head, it becomes critical to be able to predict and controlthe flow of adhesive because differences in adhesive flow anddistribution from one part to another can adversely affect thegeometries, mechanical properties, and resulting performance of thesuspension. These issues are particularly pronounced when the PZT islocated at a particularly sensitive part of the suspension such as nearor at the gimbaled head slider. Repeatability and predictability areespecially critical in that area. Still further, the presence of liquidepoxy and its dispensing equipment within the final assembly roomrepresents both a potential source of contamination, as well as anadditional and expensive manufacturing step.

Another drawback to the prior attachment means is the delays in assemblytime required for multiple rounds of epoxy, including both conductiveepoxy and non-conductive epoxy, to be dispensed and then cured. FIG. 6.illustrates the typical manufacturing process for PZT attachment, inwhich liquid epoxy is applied to the PZT, the interconnect, and/or theload beam before attaching the PZT. Conductive epoxy is dispensed at theinterconnect (610), then non-conductive epoxy is dispensed at the loadbeam or other location for the PZT (612). The PZT is attached to thesuspension (614), and the epoxy is then cured (616) in a first curingstep. Next, conductive epoxy is dispensed again (618), and then cured(620) in a second curing step.

SUMMARY OF THE INVENTION

In order to address the foregoing disadvantages and other disadvantagesof prior assembly processes, the present invention employs other typesof adhesive than those traditionally used for DSA suspensions, andbonding and curing steps other than those traditionally used for DSAsuspensions.

In one aspect, the invention employs adhesive films between the PZT andthe suspension, and/or employs partially curing (B-staging) of a liquidor paste adhesive such as epoxy on the PZT before the PZT is placed ontothe suspension component. The suspension component to which the PZT isaffixed can be a base plate such as shown in FIGS. 1 and 2 for abaseplate mounted microactuator, a flexure such as shown in FIGS. 3-5for a flexure mounted actuator, the suspension's load beam, the headslider itself in the case of a collocated PZT, or any other suspensioncomponent to which a microactuator motor may be mounted. After the twoparts have been mated, the epoxy or other adhesive is finally cured. Thecuring can be thermal curing, UV curing, or other method of curing.

In a second aspect of the invention, the invention is of a method forproducing a PZT microactuator or other electronic device having awrap-around electrode, and of applying and using such a device. Thewrap-around electrode is a conductive coating that wraps around at leastpart of the PZT to cover more than one face of the PZT, and thus conductelectricity to the opposite face. The wrap-around electrode simplifiesboth the assembly process and the final electrical connection(s) to thePZT in the completed suspensions. According to the method, a centralelectrode is first formed such as by sputtering on a first face of awafer of piezoelectric material. A first side electrode on then formedon a first side or end of the wafer and over the adjacent edge, suchthat the first electrode extends onto the first face but is electricallynot connected with, i.e., is discontinuous from, the central electrodeon that face. Similarly, a second side electrode is also formed on asecond side or end that is opposite the first side, with the secondelectrode also extending over an adjacent edge, such that the secondelectrode extends onto the first face but is also electricallydiscontinuous from the central. Conductive material is then depositedsuch as but sputtering on the second face of the wafer opposite thefirst face, with that conductive material extending to and being inelectrical contact with the first and second side electrodes. The wafernow has one central electrode on the first face that covers most of thefirst face, and two side electrodes, with each side electrode coveringnot only its respective side but wrapping around that side and coveringat least respective parts of the first and second faces, preferably atnarrow respective strips on the first face on either side of the centralelectrode. The wafer is then cut in half. The result is twopiezoelectric devices, each device having a wrap-around electrode suchthat the first face includes both electrodes. Both the drive and theground connection can therefore both be made to the first face of thePZT, thus simplifying the electrical connections to it.

The invention simplifies the assembly process for a DSA suspension, andeliminates contamination sources in the sensitive final suspensionassembly.

Exemplary embodiments of the invention will be further described belowwith reference to the drawings, in which like numbers refer to likeparts. The drawing figures might not be to scale, and certain componentsmay be shown in generalized or schematic form and identified bycommercial designations in the interest of clarity and conciseness.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a prior art disk drive assembly having aDSA suspension.

FIG. 2 is a top plan view of the prior art suspension 105 in FIG. 1.

FIG. 3 is a perspective view of a prior DSA suspension to which thepresent invention is applicable.

FIG. 4 is a sectional view taken along section line C-C′ in FIG. 3.

FIG. 5 is a sectional view taken along section line D-D′ in FIG. 3.

FIG. 6 is a process flow diagram of the process used to attach the PZTto the suspension in FIG. 3.

FIG. 7 is a process flow diagram of the simplified process used toattach a PZT to a suspension according to the invention.

FIG. 8 is a perspective view of a DSA suspension minus the flexuregimbal assembly, according to an embodiment of the present inventionthat employs integrated adhesive patterns printed onto the PZT.

FIG. 9 is an exploded view of the suspension of FIG. 8.

FIG. 10 is a perspective view of one of the PZTs of the suspension ofFIG. 8, showing the integrated adhesive film underneath.

FIG. 11 is a perspective view of a portion of a DSA suspension accordingto an additional embodiment of the invention, in which integratedadhesive film is used on the top surface of the PZT.

FIG. 12 is a perspective view of the PZT in FIG. 11.

FIG. 13 is a side cut-away view of a PZT having a wrap-around electrodeaccording to an additional embodiment of the invention.

FIG. 14 is a process flow diagram for the prior epoxy dispensing andbonding steps for the PZT of FIG. 3

FIG. 15 is a process flow diagram for the prior epoxy dispensing andbonding steps and for the PZT of the present invention shown in FIG. 13.

FIGS. 16A-16G illustrate the manufacturing steps for making the PZT withwrap-around electrode shown in FIG. 13.

FIGS. 17A and 17B are isometric views of a PZT wafer at selected stepsduring the manufacturing process according to the present invention.

FIGS. 18A-18G show an alternative manufacturing process that could beused to produce the PZT of FIG. 13.

FIG. 19 is a perspective view of a PZT with adhesive being appliedthereto according to the invention.

FIG. 20 is a top perspective view of the PZT of FIG. 19 illustrating theadhesives thereon being B-staged.

FIG. 21 is a side cutaway view of the PZT of FIG. 20 after it has beenapplied to a suspension.

FIG. 22 is a side cutaway view of the PZT having a wrap-around electrodeafter it has been applied to a suspension.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first aspect of the invention is the use of adhesive film to attachthe PZT to the suspension. FIG. 7 illustrates the method. Conductiveepoxy is dispensed at the interconnect (710). The PZT having theintegrated adhesive film or other B-staged adhesive is then attached tothe suspension (712), and the adhesive is then cured (714). Conductiveepoxy is then dispensed at (716) and cured (718). The step of epoxydispensing on the load beam is eliminated by using a PZT with integratedadhesive film. PZT with integrated adhesive film can be manufacturedwith either laminated adhesive film on it at the PZT wafer level or byprinting or by a wafer backside coating process as used in thesemiconductor industry. Because the adhesive film is attached to the PZTat the wafer level before dicing into individual PZT dies, processsimplification and cost savings can be achieved. Also, tight control ofthe adhesive thickness can be achieved. As shown in FIG. 7 the use of aPZT with integrated adhesive also simplifies the process when comparedto FIG. 6. The step of non-conductive epoxy dispensing at the load beamis eliminated using the method of the invention.

A suspension design that facilitates the use of integrated adhesive filmis shown in FIGS. 8-10. FIG. 8 is a perspective view of a DSAsuspension, less the flexure gimbal assembly for clarity ofillustration, according to an embodiment of the present invention thatemploys integrated adhesive film or patterns printed onto the PZT. PZTs830 are affixed to the suspension component to which it is mounted, inthis case to baseplate 812. Actuation of the PZTs moves load beam 820such that the head slider which is located at the distal end of the loadbeam moves radially.

FIG. 9 is an exploded view of the suspension of FIG. 8.

FIG. 10 is a perspective view of one of the PZTs 830 of suspension 810of FIG. 8, showing the integrated adhesive film or printed adhesive 834,836 underneath. In this embodiment, the integrated adhesive films 834,836 located at both ends of PZT 830 are formed by applying adhesive filmor printing adhesive patterns on the PZT wafers before dicing andsingulation into individual PZT pieces. The exposed PZT surface betweenthe adhesives will allow for electrical connection with liquid epoxy tothe suspensions's electrical circuit.

FIG. 11 is perspective view of a portion of a DSA suspension accordingto an additional embodiment of the invention, in which integratedadhesive film is used on the top surface of PZTs 1130 in order to bondthe PZTs to recessed portions of baseplate 1112.

FIG. 12 is a perspective view of the PZT in FIG. 11. In this design, theintegrated adhesive film or printed adhesive 1134 is located at the topsurface of the PZT. The integrated adhesive film covers the entire topsurface, or substantially the entire top surface, and thus no patterningof the adhesive is required. Also, conductive adhesive film can be usedin this design, such that the grounding through the base plate can beachieved once the PZT is attached to the base plate. This will furthereliminate the required step of grounding the PZT to the baseplate withconductive liquid epoxy as shown in FIG. 6.

The adhesive film used can be either conductive or non-conductive,depending on whether an electrically conductive connection to thesuspension or the interconnect circuit is desired, or a non-conductiveconnection to the suspension. Film adhesives are generally “preformed”or “B-staged,” and are available in rolls, sheets, or die-cut shapes.

B-Staged Epoxy

In a slightly different embodiment, instead of applying adhesive film tothe PZT and/or to the suspension, adhesive is applied to the PZT and isB-staged before final assembly.

The term “B-staged” or “B-staging” as used herein means, after aflowable adhesive has been dispensed, partially hardening the adhesiveso that its flow rate is substantially reduced to the point that it nolonger flows freely as a liquid, but is not so hard such that it is nolonger available for effectively adhering to another surface. B-staginginvolves temporarily exposing the adhesive to an environment whichcauses accelerated hardening of the adhesive, then removing the adhesivefrom that environment such that the hardening rate slows downconsiderably so that the adhesive does not substantially harden duringassembly. The removal of the PZT from that increased hardeningenvironment can include simply removing the hardening accelerant fromthe environment. B-staging can cure or otherwise harden the adhesive toa degree such that the adhesive is no longer tacky. One method ofB-staging is to partially cure a cross-linking polymer such as epoxy,such as by applying heat and/or UV, such that the epoxy achieves lessthan 10% cross-linking, then removing the curing source. For epoxiesthat are B-staged using heat, the epoxy may be immediately quenched downto a lower temperature at which cross-linking is negligible, i.e, atwhich the epoxy effectively ceases to harden, in order to stop thecross-linking process. For epoxies that are B-staged using UV, removingthe PZT from the increased hardening environment can mean simply turningoff the UV curing lamps.

With some adhesives, the adhesive may be mixed into a solvent to form aslurry, the solvent being one that evaporates at a lower temperaturethan which cross-linking begins to occur significantly. The adhesive maybe a printable paste that is applied to the PZT. After dispensing, theadhesive is exposed to a specified thermal regime designed to evolve amajority of the solvent from the material without significantlyadvancing resin cross-linking. The result is an epoxy or other adhesivethat no longer flows, but that is still available for adhering toanother surface with the full or nearly full adherent strength of theepoxy.

B-staging an adhesive permits the adhesive and substrate construction tobe “staged,” or held for a period of time prior to the bonding andcuring, without forfeiting performance. A secondary thermal cure cycleyields fully crosslinked, void-free bonds. As used herein, the term“fully crosslinked” means at least 90% crosslinked.

The adhesive may take the form of a solid, thermosetting paste. Theadhesive may be a printable paste that is printed by any known printingtechniques that are suitable for use with adhesive, including screenprinting, stencil printing, ink jet printing, spraying, stamping, andothers. An advantage of using such printing techniques is that theadhesive can be dispensed in very fine and precise patterns onto thePZT, which helps to achieve control and repeatability of the adhesive'stotal mass and distribution within the finished suspension. Onecommercially available silver-filled conductive epoxy that is suitablefor fluid jetting, screen printing, and stamping is EPO-TEK® H20E byEpoxy Technology, Inc. of Billerica, Mass.

A UV B-stage adhesive can be used. Such an adhesive is dispensed, thenirradiated with UV energy in order to B-stage it. B-staging immediatelyafter printing “freezes” the adhesives in position, which helps toprecisely control any spread of the liquid epoxy. Unlike thermalstaging, irradiating with UV energy eliminates the danger of advancingthe thermoset reaction of the adhesive. UV B-staging can occur inseconds, while the thermal alternative can take an order of magnitudelonger for the process.

Liquid epoxy or other adhesive may be first dispensed onto the PZTand/or onto the suspension, and then the epoxy is B-staged to the pointthat its flow is reduced to a negligible amount. The parts can then beassembled in the final, clean room assembly area for the disk drives,and the adhesive then fully cured either by heat or by UV. Suchtechniques have been used, or have been proposed to be used, in theintegrated circuit (IC) packaging field under the broad term of waferbackside coating (WBC). Wafer backside coating techniques using bothconductive and non-conductive adhesives can be adapted from die attachprocesses used in IC packaging to PZT attach processes for suspensions.Inkjet printing of polymers, both conductive and non-conductive, hasalso been proposed. Such inkjet printing techniques can be adapted foruse in printing adhesives onto the PZTs for bonding those PZTs tosuspensions.

It is anticipated that one method of production will be to begin with awafer of PZT material, either applying already B-staged adhesive to itsuch as in adhesive film form or applying adhesive to it then B-stagingthe adhesive, then dicing the wafer into individual PZT microactuatormotors. Pick-and-place machinery will be used to pick up the individualPZT die with the B-staged adhesive on it, assemble the PZT die to thesuspension, and dwell there for the appropriate time and under theappropriate temperature and pressure conditions in order to fully curethe adhesive, and thus fully adhere the PZT to the suspension.

Wrap-Around Electrode

In another aspect, the invention is of a method of producing apiezoelectric microactuator or other electronic device having awrap-around electrode, such that both the drive voltage and groundelectrodes are located and accessible on the same side of the device.

FIG. 13 is a side cut-away view of a PZT according to an additionalaspect of the invention. PZT 1330 has a bottom electrode 1334 and a“wrap-around” electrode 1336 that enables simplified electricalconnections to the PZT. In this embodiment, the top electrode 1336 iswrapped around the PZT onto one end of the bottom PZT surface. Thedriving voltage is thus applied to the bottom surface of the PZT on afirst end thereof, and the electrical ground is connected to the bottomsurface on the opposite end. Thus, both electrodes 1334, 1336 can beelectrically connected by conductive epoxy 1340, 1342, respectively, onthe same surface or side of the PZT. This reduces the number of epoxybonding steps to two steps and eliminates the difficult to control epoxyheight tolerance on the top PZT surface. Also, only a single curing stepis needed.

FIG. 14 is a flow diagram of a manufacturing process using prior epoxydispensing and bonding steps for attaching the PZT to its suspension asshown in FIG. 3. Conductive epoxy is first dispensed for grounding(1410). Non-conductive epoxy is then dispensed for insulation (1412).The PZT is then attached to the suspension, at step 1414. The epoxiesare then cured (1416). A second epoxy dispensing step is then performed(1418). Finally, that last-dispensed epoxy is cured (1420). The processrequired two separate curing steps.

FIG. 15 is a flow diagram of a manufacturing process according to thepresent invention for bonding the PZT to its suspension as shown in FIG.13. Conductive epoxy is dispensed for grounding (1510). Conductive epoxyis then dispensed for the signal or driving voltage for the PZT (1512).The PZT is then attached to the suspension (1514). Finally, the assemblyis cured (1516). The figures illustrate the simplification that isobtained by using a PZT with a wrap-around electrode according to theinvention.

FIGS. 19-21 illustrate the preparation and placement of a PZT havingB-staged adhesive according to the invention. FIG. 19 is a perspectiveview of a PZT 1930 with adhesive 1920, 1924 being applied to what willbe the bottom surface of PZT 1930. In general, the adhesive can beapplied by any one of a number of known techniques including screenprinting, stencil printing, ink jet printing, spraying, application as afilm, and others. In general, any patterns desired of a combination ofconductive adhesive and/or non-conductive adhesive may be applied to PZT1930. In the illustrative embodiment shown, the adhesive is sprayed byink jet heads 1910, 1911, to produce one strip of conductive epoxy 1924,and one strip of non-conductive epoxy 1920. The two strips can be ofdifferent thicknesses, with one strip being thicker than the other.

FIG. 20 is a top perspective view of PZT 1930 with the adhesives beingB-staged. In the figure, the epoxy strips 1920, 1924 are being UVB-staged. In general, adhesives 1920, 1924 can be B-staged using anyknown technique including thermal B-staging and UV B-staging.Furthermore, the two strips of adhesive 1920, 1924 can be B-staged todifferent extents, leaving one strip more cured or hardened than theother. For UV curing, masks or screens can be used in order to irradiateone strip more than the other.

FIG. 21 is a side cutaway view of PZT 1930 after it has been applied toa suspension. FIG. 21 is analogous to FIG. 3 and illustrates how thepresent invention can simplify the prior process. After PZT 1930 hasbeen positioned, pressure is applied to at least the left side of thePZT as seen in the figure in order to squeeze non-conductive epoxy 1920so that it flows into the gap between the PZT and polyimide layer 314,and covers the previously exposed stainless steel 312 adjacent the PZT.The pressure could be applied by mechanically pressing on the PZT.Alternatively, depending on how much hardening occurred during theB-staging process, the weight of the PZT itself may provide sufficientforce and pressure to squeeze non-conductive epoxy 1920 into that gap.After the PZT is positioned, and pressed down if necessary, conductiveepoxy 322 is applied so as to bridge the gap between the metallized topsurface of the PZT, which defines the drive electrode, and coppercontact pad 316 which supplies the drive voltage to the PZT. All of theepoxy in the assembly is then cured at the same time in a single curingstep. This process eliminates the need for a second curing step as wasrequired for the assembly and process of FIGS. 3-6.

FIG. 21 represents only one of a number of possible different types ofelectrical connections and electrical connection methods for providingthe PZT driving voltage and ground to the PZT. Many other connectiontypes and methods are possible, such as disclosed in U.S. Pat. No.8,189,301 to Schreiber, and U.S. Pat. No. 7,751,153 to Kulangara. Thepresent invention is applicable in suspensions that employ various typesof electrical connections to the PZTs.

As an alternative to the bonding structure shown in FIG. 21, PZT 1930could be extended farther to the left in the figure, such that the PZTis bonded directly to copper contact pad 316.

FIGS. 16A-16G illustrate the manufacturing steps for making the PZT withwrap-around electrode shown in FIG. 13. First, a PZT block or wafer 1630is placed onto a transfer tape 1602, with PZT bottom surface 1631 facingdownward (FIG. 16A). Next, an appropriate mask is placed over the topsurface of the PZT wafer, and a metallization layer 1604 such asaluminum metallization is sputtered onto the top surface (FIG. 16B). Themask leaves strips 1606 of PZT surface not metallized. Kerf 1608 is thencut into the PZT wafer to separate a first portion, which will bereferred to as a PZT precursor 1632, from the rest of the wafer (FIG.16C). A second mask 1612 is placed over PZT precursor 1632, andadditional metallization 1605 is sputtered into the kerfs onto the sidesof PZT precursors 1632 within kerfs 1608 in order to make those sideselectrically conductive and electrically continuous with themetallizations on the top surface of the PZT adjacent the kerfs (FIG.16D).

Next, the PZT precursor 1632 is flipped over and preferably placed ontoa second transfer tape in order to expose what had been the bottomsurface 1631 of the PZT precursor (FIG. 16E). That bottom surface 1631will continue to be referred to as the bottom surface even though it isnow facing upward. A metallization layer 1614 is then sputtered onto theentire bottom surface 1631 of the PZT precursor (FIG. 16F). Finally, anew cut 1616 is made into the PZT, separating the first PZT generally inhalf and defining what will be referred to as first PZT 1634 and secondPZT 1636 (FIG. 16G).

The result of this process is two PZTs 1634, 1636 each of which has thesame structure. A narrow stripe of metallization 1650 on the first PZT'stop surface 1633 and near its end, defines a first electrode. The firstelectrode 1650 electrically wraps around via the metallized side surface1605 of the PZT to the bottom surface 1631 of the PZT and to themetallization 1604 that generally covers bottom surface 1631. A secondelectrode 1652 on the top surface 1633 of the first PZT covers most, butnot all, of the PZT top surface 1633. In this way, a first PZT has beenconstructed whose first electrode 1650 is located on the same surface ofthe first PZT as the second electrode 1652. Generally speaking, thefirst electrode can be the electrode at which the PZT drive voltage isapplied with the second electrode being the electrode at which the PZTis grounded, or vice versa. The second PZT is substantially identical tothe first PZT.

FIGS. 17A and 17B are isometric views of a PZT wafer at selected stepsduring the manufacturing process according to the present invention.FIG. 17A is an isometric view of the PZT strips 1634, 1636 at the end ofthe process in FIG. 16. Now, the PZT is ready for poling; the finaldicing operation can be performed afterward to create the individualPZTs as shown in FIG. 17B. The result is a first row of PZTs 1638 and asecond row of PZTs 1640, both having wrap-around electrodes.

FIGS. 18A-18G illustrate alternative manufacturing steps for making thePZT having a wrap-around electrode. The PZT wafer 1830 is placed onto atransfer tape 1802 with its bottom surface 1831 facing downward (FIG.18A). Kerfs 1808 are then cut into PZT 1830 to separate a first portion,which will be referred to as a PZT precursor 1832, from the rest of thewafer (FIG. 18B). The kerfs 1808 on either side of PZT precursor 1832are then filled with a conductive and hardenable material 1820, such asconductive epoxy paste containing copper, silver, or other conductivematerial or particles (FIG. 18C). Silver epoxy is one such commonly usedmaterial, and will be used as an example. Silver epoxy 1820 is thenallowed to harden. Next, an appropriate mask is placed over the topsurface of PZT precursor 1832, and a metallization layer 1804 such asaluminum metallization is sputtered onto the top surface (FIG. 18D). Themask prevents metallization along two narrow strips 1806, 1807 on thetop surface of the PZT precursor near the ends thereof. The result isthat the PZT precursor 1832 has two relatively narrow stripes ofmetallization 1842, 1844 on the top surface of the PZT precursor neareither end thereof, and a large metallization area 1846 generallycentered on the PZT precursor. At this point in the process, each stripeof metallization 1842, 1844 near an end of the PZT precursor iselectrically connected to the silver epoxy 1820 on the end of the PZTprecursor to which that stripe is adjacent, and each of the two stripesof metallization 1842, 1844 and the large metallized region 1846 in thecenter are all electrically isolated or electrically discontinuous fromeach other.

Next, the PZT precursor is flipped over and preferably placed onto asecond transfer tape in order to expose what had been the bottom surface1831 of the PZT precursor (FIG. 18E). That bottom surface 1831 willcontinue to be referred to as the bottom surface even though it is nowfacing upward. A metallization layer 1814 is then sputtered onto theentire bottom surface of the PZT precursor (FIG. 18F). Finally, a newcut 1818 is made into the PZT precursor, cutting the PZT precursorgenerally in half, and another cut 1816 is made through the silverepoxy, thereby separating the PZT precursor in half and defining whatwill be referred to as first and second PZTs (FIG. 18G). The cut 1816 iswithin kerf 1808 and is narrower than kerf 1808 so as to leave the sideof the PZT precursor covered with conductive silver epoxy 1820, and thusserves as an electrical bridge or wrap-around from the PZT's top surfaceto its bottom surface.

The result of this process is two PZTs each of which has the samestructure. A narrow stripe of metallization 1844 on the first PZT's topsurface 1833 and near its end, defines a first electrode. The firstelectrode 1844 electrically wraps around via the silver epoxy 1820 tobottom surface 1831 of the PZT and to the metallization that generallycovers bottom surface 1831. A second electrode 1852 on the top surface1833 of the first PZT covers most, but not all, of the PZT top surface1833. In this way, a first PZT has been constructed whose firstelectrode 1844 is located on the same surface of the first PZT as theopposite electrode 1852. The second PZT is substantially identical tothe first PZT.

FIG. 22 is a side cutaway view of the PZT having a wrap-around electrodesuch as the PZTs of either FIG. 16G or FIG. 18G, after it has beenapplied to a suspension. PZT 1830 has a first and wrap-around electrode1844 which serves as the drive or positive electrode, and a secondelectrode 1852 which serves as the ground electrode. Drive electrode1844 is bonded to copper contact pad 316 on polyimide layer 314 overstainless steel substrate 312, via conductive epoxy 1924. Groundelectrode 1852 is grounded to stainless steel substrate 328 via goldbond pad 326 and conductive epoxy 1928. Strips of conductive epoxy 1924and 1928 can be B-staged epoxies as discussed above, with the epoxiesfully cured after the parts have been assembled as shown in the figure.This embodiment completely eliminates the need to dispense any epoxywithin the suspension assembly room, and eliminates any liquid or pasteepoxy from that room, and thereby helps to keep that environment freefrom contamination.

It will be understood that the terms “generally,” “approximately,”“about,” and “substantially,” as used within the specification and theclaims herein allow for a certain amount of variation from any exactdimensions, measurements, and arrangements, and that those terms shouldbe understood within the context of the description and operation of theinvention as disclosed herein.

It will further be understood that terms such as “top,” “bottom,”“above,” and “below” as used within the specification and the claimsherein are terms of convenience that denote the spatial relationships ofparts relative to each other rather than to any specific spatial orgravitational orientation. Thus, the terms are intended to encompass anassembly of component parts regardless of whether the assembly isoriented in the particular orientation shown in the drawings anddescribed in the specification, upside down from that orientation, orany other rotational variation.

All features disclosed in the specification, including the claims,abstract, and drawings, and all the steps in any method or processdisclosed, may be combined in any combination, except combinations whereat least some of such features and/or steps are mutually exclusive. Eachfeature disclosed in the specification, including the claims, abstract,and drawings, can be replaced by alternative features serving the same,equivalent, or similar purpose, unless expressly stated otherwise. Thus,unless expressly stated otherwise, each feature disclosed is one exampleonly of a generic series of equivalent or similar features.

It will be appreciated that the term “present invention” as used hereinshould not be construed to mean that only a single invention having asingle essential element or group of elements is presented. Similarly,it will also be appreciated that the term “present invention”encompasses a number of separate innovations which can each beconsidered separate inventions. Although the present invention has thusbeen described in detail with regard to the preferred embodiments anddrawings thereof, it should be apparent to those skilled in the art thatvarious adaptations and modifications of the present invention may beaccomplished without departing from the spirit and the scope of theinvention. For example, instead of selectively applying and partiallycuring adhesive on the PZT, adhesively could be selectively applied andpartially cured on other suspension components such as the flexure.Accordingly, it is to be understood that the detailed description andthe accompanying drawings as set forth hereinabove are not intended tolimit the breadth of the present invention.

We claim:
 1. A method of manufacturing a piezoelectric microactuator,the method comprising: (a) forming a central electrode on a first faceof a wafer of piezoelectric material, the wafer having opposite firstand second faces and opposite first and second sides, the wafer furtherhaving first and second edges where the first face and second meets thefirst and second sides, respectively; (b) forming a first side electrodeon the first side and over the first edge, the first side electrodeextending onto the first face but being electrically discontinuous fromthe central electrode; (c) forming a second side electrode on the secondside and over the second edge, the second side electrode extending ontothe first face but being electrically discontinuous from the centralelectrode; (d) depositing a conductive material on the second face ofthe wafer opposite the first face, the conductive material extending tothe first and second side electrodes; (e) whereby the wafer has acentral electrode on the first face thereof, and first and second sideelectrodes each of which wraps from the first face around respectiveopposite sides of the wafer and to the second face; (f) cutting thewafer into two piezoelectric devices, each piezoelectric device havingtwo electrodes, a first of which is located on the first face and asecond of which wraps around from first face of the piezoelectric deviceto the opposite and second face thereof.
 2. The method of claim 1wherein the central electrode is formed by sputtering with a mask toform the central electrode and respective portions of the two sideelectrodes on either side of the central electrode, each of the two sideelectrode portions being electrically discontinuous from the centralelectrode.
 3. The method of claim 2 wherein step (b) includes: applyinga mask to the first face; sputtering metallization onto the first faceof the wafer; cutting a kerf into the wafer; and sputteringmetallization onto the first and second edges of the wafer.
 4. Themethod of claim 3 further comprising: before step (a), placing the waferon a transfer tape with the second face of the wafer facing the tape;and before step (d), flipping the wafer over so that its first face isfacing downward.
 5. The method of claim 2 wherein step (b) includes:cutting first and second kerfs in the wafer; filling the kerfs withconductive paste and hardening the paste; applying a mask to the firstface and sputtering metallization onto the face and onto the conductivepaste to form the central electrode and the two side electrodes, the twoside electrodes being electrically discontinuous from the centralelectrode; and cutting third and fourth kerfs within the first andsecond kerfs, respectively, the third and fourth kerfs being narrowerthan the first and second kerfs, leaving the first and second ends ofthe wafer covered with the conductive paste after the third and fourthkerfs are cut.
 6. A method of manufacturing a piezoelectricmicroactuator, the method comprising: (a) forming a kerf in apiezoelectric block to separate the piezoelectric element into at leastfirst and second piezoelectric elements, the kerf extending from a topsurface of the first piezoelectric element to a bottom surface thereof;(b) applying a first conductive material into the kerf; (c) applying asecond conductive material to the top surface of the first piezoelectricelement so as to cover both a majority of the top surface of the firstpiezoelectric element, and so as to establish electrical connectivitybetween the first conductive material in the kerf and at least a portionof the top surface adjacent the kerf; (d) forming an electricaldiscontinuity in the second conductive material so as to electricallyisolate said second conductive material covering the majority of the topsurface from said portion of the second conductive material adjacent thekerf; (e) applying a third conductive material on the bottom surface ofthe first piezoelectric element, the third conductive materialestablishing electrical connectivity between said bottom surface and thefirst conductive material in the kerf; (f) whereby electricalconnectivity is established between the bottom surface of the firstpiezoelectric element and at least said portion of the top surfacethereof adjacent the kerf, and electrical connectivity is notestablished between the bottom surface of the first piezoelectricelement and said majority of the top surface, thereby defining a firstpiezoelectric element having a wrap-around electrode.
 7. The method ofclaim 6 further comprising: (g) cutting the first conductive materialwithin the kerf thereby separating the first and second piezoelectricelements, a first half defining a first piezoelectric microactuatorhaving a first electrode on a majority of its top surface, and furtherhaving a second electrode on its bottom surface that wraps around to atleast a portion of its top surface, the first and second electrodesbeing electrically discontinuous and defining first and secondelectrodes for actuating the microactuator by applying an electricpotential across the first and second electrodes, and wherein theelectric potential may be applied across two points both of which are onthe top surface of the piezoelectric microactuator.
 8. The method ofclaim 7 further comprising: (h) cutting through the first piezoelectricelement at a locus within said majority of the top surface therebyseparating the first piezoelectric element into first and second halves,the two halves defining first and second microactuators each havingtheir own wrap-around electrodes.
 9. The method of claim 6 wherein thefirst conductive material in the kerf is hardenable conductive adhesive,and the second and third conductive materials are metallization layers.10. The method of claim 6 further comprising: (i) after steps (c) and(d) but before step (e), flipping the first piezoelectric elementthereby exposing the bottom surface therefore for application of thethird conductive material thereto.